The present invention is generically directed to mechanical links between modules of a hearing aid apparatus, so as to construe the hearing aid apparatus or between a hearing aid apparatus and an additional appliance.
It is further directed to a technique for establishing an electrical connection, again either between modules concomitantly defining the hearing aid apparatus or between a hearing aid apparatus and an additional appliance.
It is known from the U.S. Pat. No. 6,157,728 to transmit electrical signals to a therapeutical outside-the-ear hearing aid apparatus via an inductive link. In the transmission cable as an additional appliance to the hearing aid apparatus there is provided an induction coil wound around a cylindrical magnet. The axis of the cylindrical magnet is perpendicular to a surface along which the cable's plug is applied to the hearing aid apparatus. Within the hearing aid apparatus there is provided a disk-shaped ferromagnetic plate adjacent to the respective surface of the hearing aid apparatus, to which the plug is to be joined. The cylindrical magnet, on the one hand, and the disk-shaped ferromagnetic plate, on the other hand, simultaneously form the mechanical link between the appliance and the hearing aid apparatus and the electrical inductive connection between the appliance and electronic components within the hearing aid apparatus.
Thereby, analogue signals as audio signals are transmitted between the inductive link of induction coil with cylindrical magnet core on the side of the appliance and ferromagnetic plate as receiver part on the side of the hearing aid apparatus.
Although being advantageous with respect to easy mechanical linking of the appliance to the hearing aid apparatus by the user carrying the hearing aid apparatus at his ear, this technique suffers different drawbacks:                Due to the arrangement of the ferromagnetic plate perpendicularly to the axis of the cylindrical magnet, once the appliance is mounted to the hearing aid apparatus, this ferromagnetic plate considerably shunts and thus dampens in particular high frequency signals to be transmitted.        Due to the fact that the ferromagnetic plate has two objects, namely contributing to the mechanical link as well as contributing to the electric signal transmission, a compromise solution as with respect to the material of the ferromagnetic plate on the one hand for signal transmission, on the other hand for mechanical linkage purposes must be made, which may not be optimum for both objects.        Due to the inductive link, whereat parts, namely the ferromagnetic plates, are used for both objects, namely mechanical and electrical link, there is an interdependency between mechanical and electrical link quality, which, as was said, may not be construed optimally for both purposes.        